This invention relates to a process for curing resin-bonded refractory brick lined ladles, and apparatus therefore.
Traditionally, the refractory brick used to line ladles of use in EAF (electric arc furnace) operations was a pre-fired high alumina type brick, which had the tendency to be attacked by the chemically alkaline EAF slag and molten metal in the ladle. Thus, the life of the brick was short and, in consequence, had to be replaced, often, at high expense in time, effort and cost.
The aforesaid alumina brick has since been replaced by an organic resin-bonded brick, which is cheaper than the alumina brick, is more resistant to chemical attack by EAF slag and molten metal and, thus, lasts longer. It is also more readily available on demand to eliminate the need to stock the brick in inventory.
Unfortunately, the resin-bonded brick requires a longer dry-out period, and, in such drying process, smelly fumes of toxic organic chemicals, such as, benzene, phenol, formaldehyde, other hydrocarbons and carbon deposits are produced, which create an unpleasant and environmentally unsafe atmosphere. Complaints such as nausea, headache and eye and throat irritation are merely noticeable manifestations of the dangers. Since in a typical 150 tonne (150,000 kg) ladle, the refractory lining could contain in excess of 90 kgs of organic compounds, a process is required to address the curing treatment of the resin-bonded brick to prevent the aforesaid disadvantages.
However, the apparatus and process recently introduced to eliminate the toxic compounds in the emissions has been shown to be ineffective by reasons of being unreliable, inefficient and requires significant maintenance. Specifically, cooling of the organic fumes causes condensation and solidification onto equipment, such as, blowers, valves, pipes and the like which, over time, become plugged and inoperative.
There is, therefore, a need for apparatus and process for the removal of the toxic organic fumes produced by the drying process of resin-bonded refractory bricks which does not create an environmentally unsafe atmosphere or cause plugging and unwanted deposition of condensed fumes.
It is an object of the present invention to provide a process for the drying of resin-bonded refractory bricks which does not create an environmentally unsafe environment for process workers or plugging of process equipment.
It is a further object to provide apparatus for use in the aforesaid process.
Accordingly, in one aspect the invention provides an improved process of curing resin-bonded refractory brick lining of a ladle within a housing, by heating said brick in air at an effective temperature to produce resin vapors and transferring said vapors from said lining, the improvement comprising transferring said vapors at a temperature above the condensation temperature of said transferred vapors to an auxiliary burner to effect combustion of said transferred vapors to produce non-toxic gases.
In preferred embodiments, the process is as hereinabove defined wherein the vapors are produced, transferred and combusted at a negative pressure differential within the housing relative to outside of the housing as to reduce unwanted vapor leakage from the housing.
In more preferred practical embodiments, the vapors are produced, transferred and combusted at a pressure of less than atmospheric.
In a preferred aspect, the invention provides an improved process of curing resin-bonded refractory brick lining of a ladle within a housing by heating said brick in air at an effective temperature to produce resin vapors and transferring said vapors from said ladle; the improvement comprising
(i) transferring said vapors to an auxiliary burner to affect combustion of said transferred vapors to produce non-toxic gases;
(ii) drawing said transferred vapors to said auxiliary burner under suction by suction means to create a negative pressure differential value of said transferred vapor relative to atmospheric;
(iii) measuring the pressure differential value of said transferred vapors relative to atmospheric;
(iv) feeding said pressure differential value to central processing means;
(v) controlling by said central processing means said suction means to control the pressure differential value of said vapors at a desired negative value;
(vi) measuring the temperature value of said transferred vapors;
(vii) feeding said temperature value to said central processing unit; and
(viii) controlling by said central processing means the amount of air to said ladle to maintain said transferred vapors above the condensation temperature of said vapors.
In a further aspect, the invention provides apparatus for the curing of resin-bonded refractory brick lining of a ladle within a housing, comprising means for heating said brick in feed air at an effective temperature to produce resin vapors and means for transferring said vapors as transferred vapors from said ladle, the improvement comprising means for maintaining said transferred vapors above the condensation temperature of said vapors, auxiliary burner means for burning said transferred vapors to produce non-toxic gases therefrom; and means for transferring said transferred vapors to said auxiliary burner means.
In a preferred further aspect, the invention provides apparatus for the curing of resin-bonded refractory brick lining of a ladle within a housing, comprising means for heating said brick in air at an effective temperature to produce resin vapors and means for transferring said vapors as transferred vapors from said ladle; the improvement comprising
(a) an auxiliary burner to affect combustion of said transferred vapors to produce non-toxic gases;
(b) suction fan means for transferring said transferred gases to said auxiliary burner under a desired negative pressure differential value relative to atmospheric;
(c) pressure measuring means for determining said pressure differential value;
(d) temperature measuring means for determining the temperature of said transferred vapors;
(e) air inlet means for providing air to said housing; and
(f) central processing means in communication with said suction means, said air inlet means, said temperature sensing means and said pressure measuring means and for controlling said suction means and said air inlet means for maintaining said desired negative pressure differential value and said temperature of said transferred vapors above the condensation temperature of said vapors.
The preferred process and apparatus according to the invention comprises a fossil fuel combustion burner.
Thus, it has been found that suitable measurement, interrelated manipulation and subsequent resultant control of the process parameters, such as temperature, pressure and air flow rates provides for an efficacious and environmentally sound resin curing process.